At present, as a process for producing fine devices such as semiconductor devices, integrated circuits, devices for organic EL display, it is common to employ a method wherein a thin film of a functional material is formed on a substrate by e.g. vacuum deposition or sputtering, and the thin film is subjected to patterning by photolithography. The photolithography comprises the following steps (1) to (3):
(1) A thin film of a material for patterning is formed on a substrate. (2) A photoresist film is formed on the thin film, and exposure is carried out through a photomask having a predetermined pattern, followed by development with an alkaline developer to form a photoresist pattern. (3) Etching is carried out by using the photoresist pattern as a mask, and an unnecessary part is removed to obtain a thin film having a predetermined pattern configuration. Since the process steps are complex and they have to be carried out in a clean room, the photolithography has had a problem such that the utilization efficiency of energy, material, etc. is low, or the facility tends to be expensive.
A patterning method requiring low cost and energy, has been proposed. For example, ink-jet printing of a solution of a functional material (Non-Patent Document 1) or micro-contact printing (Non-Patent Document 2) is being utilized.
Recently, a method has been proposed wherein patterns having different surface characteristics are formed on a substrate, and by utilizing such a difference in the surface characteristics, a fine device is produced. For instance, there is a method wherein a hydrophobic region and a hydrophilic region are formed on a substrate, and an aqueous solution of a functional material is applied on the hydrophilic region. In such a method, the aqueous solution will spread over the hydrophilic region, and it will not exude on the hydrophobic region, whereby a thin film pattern of the functional material can be formed.
As a method for forming regions having different surface characteristics, a method wherein on a substrate having a certain characteristic 1, a thin film having another characteristic 2 is formed, and a part of the thin film is removed to expose the surface having the characteristic 1 thereby to form a surface having the characteristic 1 and characteristic 2, or a method wherein on a region where the thin film having the characteristic 2 is removed, a thin film having a characteristic 3 is formed so as to form a surface having the characteristic 2 and characteristic 3 (Patent Document 1), has been proposed.
The thin film having the characteristic 2 can be removed more efficiently when it is thinner. Accordingly, Self-Assembled Monolayer=SAM (hereinafter referred to as SAM) is preferred. As a patterning method for a thin film such as SAM, a method employing a scanning probe microscope, or a method employing a high energy beam such as ultraviolet light or X-ray, an electron beam, a high-power laser or the like, is known. Among them, a patterning method employing ultraviolet light is preferred in manufacturing, since a substrate having a large area can be treated at once by employing a photomask. However, heretofore, a high energy beam having a wavelength of at most 200 nm has been mainly employed as ultraviolet light, and, for example, in a case where a silicon wafer substrate having a silicon oxide film formed thereon is used, there has been such a problem that even Si—O bond of the substrate is decomposed (Patent Document 2).
As a material which is capable of forming a thin film on a substrate and can be degraded efficiently at a wavelength of at least 300 nm, a 4,5-dimethoxy-2-nitrobenzyl ether compound is known, but the water repellency was not sufficient (Non-Patent Document 3).
Patent Document 1: JP-A-2002-19008
Patent Document 2: JP-A-2000-282240
Non-Patent Document 1: A. V. Lemmo, J. T. Fisher, H. M. Geysen, D, J. Rose, Anal. Chem, 1997, 69, 543-551.
Non-Patent Document 2: Y. Xia, G. M. Whitesides, Angrew. Chem. Int. Ed, 1998, 37, 550-575.
Non-Patent Document 3: Ozaki J, Yamaguchi K, Polymer Material Forum (2002), 305-306.